Preventive and persuasive actions against drunk driving

ABSTRACT

A vehicle safety system is provided that includes an alcohol concentration determining arrangement. A control unit is adapted to receive and analyze data from the alcohol concentration determining arrangement and output a blocking signal or a dissuasion signal under certain conditions. A blocking arrangement is adapted to prevent driving of the vehicle by the vehicle occupant upon receipt of a blocking signal. A output device is adapted to receive the dissuasion signal and to present a warning to the vehicle occupant to dissuade the occupant from driving the vehicle. The control unit is operable to categorize the concentration of alcohol in the occupant&#39;s blood into one of three categories: a low concentration category, in which the blocking signal will not be generated, a high concentration category, in which the blocking signal will be generated, and an intermediate category, in which the dissuasion signal will be generated.

THIS INVENTION is concerned with methods and devices aiming at theprevention of traffic accidents due to drunk driving. More specifically,the methodology relates to breath analysis for the presence andconcentration of alcohol, and to preventive or persuasive means in thecase of positive outcome of the analysis. In Anglo-Americannomenclature, the type of device is normally referred to as alcoholinterlock, or the shorter term alcolock. The preventive effect of thesedevices have been demonstrated, along with several positive sideeffects, especially for the rehabilitation of drivers already convictedfor drunk driving, and as a tool for quality assurance of transportationservices.

The purpose of an alcohol interlock is to prevent drunk driving.Technically, this is implemented by disabling the start of the engine,unless a breath sample with no or little alcohol concentration has beenprovided. A drunk person with affected driving capability and judgementis thus physically prevented from driving, thereby eliminating possibledamage to life and property caused by driving influenced by alcohol. Theconcentration limit determining whether the alcohol interlock isblocking or unblocking normally coincides with the limit, above whichdriving is illegal.

Regardless of its obvious merits, the idea of alcohol interlocks issomewhat controversial from the point of view of personal integrity andresponsibility. A vehicle owner could conceive the alcohol interlock asrestricted access to private property, and hence an infringement onpersonal integrity. A person caught for drunk driving may claim at leastpartial irresponsibility, if the vehicle was equipped with an alcoholinterlock and still driveable. It should be noted that both issues ofintegrity and responsibility touch upon the possibility of falseblockings and unblockings. Suppliers of alcohol interlocks areinvariably vague about the influence of inevitable measurement errors,which certainly will cause false outputs at a rate depending on theerror magnitude. A highly precise instrument will give rise to few falseoutputs. If many drivers make use of this precision to drive slightlybelow the limit rather than refraining from driving, the number ofintoxicated drivers may increase rather than decrease, thus partlyundermining the purpose of alcohol interlocks. On the other hand, adevice with a large error will frequently block falsely. If routes tocircumvention are introduced to alleviate this problem, the main purposewill again be undermined.

Cost, inconvenience and time consumption are common additional argumentsagainst alcohol interlocks, especially from drivers who are moderateconsumers of alcohol. The possibility of circumvention or manipulation,e g by asking someone else to provide the breath sample or bypassing theinterlock, is another problem.

The issues and problems outlined above are not the topic of publicdiscussion, but their relevance and importance should become obvious toanyone after careful consideration, since they concern basic functionand characteristics of alcohol interlocks and related devices.

The present invention aims to address these issues and problems.Accordingly, one aspect of the present invention provides a vehiclesafety system, comprising: an alcohol concentration determiningarrangement, for making a determination as to the concentration ofalcohol in the blood of a vehicle occupant; a control unit adapted toreceive and analyse data from the alcohol concentration determiningarrangement, and in dependence upon the results of the analysis,operable to output a blocking signal or a dissuasion signal; a blockingarrangement, adapted to receive the blocking signal and to preventdriving of the vehicle by the vehicle occupant; and an output deviceadapted to receive the dissuasion signal and to present one or morewarnings to the vehicle occupant to dissuade the occupant from drivingthe vehicle; wherein: the control unit is operable to categorise theconcentration of alcohol in the occupant's blood into one of threecategories, comprising a low concentration category, in which theblocking signal will not be generated, a high concentration category, inwhich the blocking signal will be generated, and an intermediatecategory, in which the blocking signal will not be generated and thedissuasion signal will be generated.

Advantageously, the alcohol concentration determination arrangementanalyses a sample of the occupant's breath.

Preferably, the warning output by the output device comprises auditory,visual and/or haptic stimulation.

Conveniently, the output of the output device comprises one or more ofthe illumination of a light source, the generation of a sound, thegeneration of a verbal message, the display of text, or vibratorystimulation of a part of the driver's body.

Advantageously, the output of the output device varies depending uponthe concentration of alcohol in the occupant's blood.

Another aspect of the present invention provides a method of controllingvehicle systems, comprising: determining a concentration of alcohol inthe blood of a vehicle occupant; categorising the concentration ofalcohol in the occupant's blood into one of three categories, comprisinga low concentration category, an intermediate category, and a highconcentration category; if the determined concentration of alcohol inthe blood of the occupant falls into the high concentration category,preventing the driving of the vehicle by the occupant; and if thedetermined concentration of alcohol in the blood of the occupant fallsinto the intermediate category, allowing the vehicle occupant to drivethe vehicle, and presenting one or more warnings to the vehicle occupantto dissuade the occupant from driving the vehicle.

Preferably, if the concentration of alcohol in the occupant's blood isdetermined to fall into the low category, the warnings are not presentedto the vehicle occupant.

A further aspect of the present invention provides a computer programcomprising computer program code adapted from all of the steps of theabove when said code is run on a computer.

Another aspect of the present invention provides a computer programaccording to the above, embodied on a computer readable medium.

A further aspect of the present invention provides a method and systemfor the prevention and persuasion of driving a vehicle under theinfluence of alcohol, characterised in the control of driveability ofsaid vehicle into three categories of unrestricted unblocking,restricted unblocking and blocking, respectively, based on the passingof system self-test, the approval of breath sample, and on the alcoholconcentration of said breath sample being correspondingly categorisedinto low, moderate and high.

Conveniently, said system self-test includes means to differentiatebetween several categories of technical error and attempts atcircumvention or manipulation, each of said means leading to differentcategories of driveability, whereby unprovoked technical error normallyleading to the category of restricted unblocking, whereas attempts atcircumvention or manipulation leading to the category of blocking.

Advantageously, said category of restricted driveability includes meansof persuasion or discomfort, by auditory, visual and haptic stimulationintended to provoke the attention of said driver, preferably withintensity and persuasiveness increasing with increasing alcoholconcentration, and on elapsed time from said breath sample acceptance,for example exerted by flashing source of light, high-intensity tone ofsound at audible frequency or infrasound, verbal message urging personto stop vehicle, communicated as display text or by artificial voice,vibratory means exerted at or within the driver's seat, and theactivation of warning blinker intended to provoke the attention of otherroad-users.

Preferably, first and second distinct limit values of breath alcoholconcentration are defined separating said categories of concentration,that at said category of moderate concentration, significant reductionof capability to handle critical traffic situations in a normal personis known to occur, at said category of high concentration, significantimpairment of judgement is known to occur, said first and second limitdiffering by at least a factor of two, and coinciding with common legalconcentration limits, said first and second operational limits being 0.1and 0.25 mg/l, respectively.

Advantageously, the probability of false blockings/unblockings does notexceed 1%.

Preferably, said breath sample approval is determined by measurementsperformed at or in the close vicinity of the mouth of said person,indicating a source of air with alveolar composition with respect tocarbon dioxide concentration, humidity, temperature or any combinationof these entities, including timing relations.

Conveniently, said breath sample approval is influenced by signalsindicating conditions of said vehicle, including opening/closure of mainlock to said vehicle, opening/closure of door to driver's seat,attachment/detachment of driver's seat belt, and position of ignitionkey.

Advantageously, determination of said alcohol concentration is a basedon the measurement of infrared absorption within wavelength intervalknown to possess absorption properties specific to alcohol.

Preferably, said driveability is controlled by actuation onto ignitionkey, solenoid, start motor, fuel injection unit, steering wheel, or gearcontrol of said vehicle.

Conveniently, said category of unprovoked errors is localised to theinternal hardware or software of said system, whereas said category ofprovoked errors being localised to the boundaries of said system withrespect to the vehicle system, the sensors, or the user interface.

Advantageously, the sensor unit includes sensor elements responding toalcohol concentration, and any combination of tracer signals of carbondioxide concentration, humidity and temperature, computational unitincluding means for the execution of pre-programmed arithmetic, logicaland sequential operations, memory unit for temporary or permanentstorage of information, user communication unit for the display ortransfer of information relevant to said driver and receiving inputcontrol signals from said driver, vehicle interface for signal transferbetween said computational unit and actuator unit for the control ofsaid driveability categories.

Preferably, the system further comprises housing adapted for single-handoperation by said driver, said housing accommodating said sensor anduser communication units, docking station for permanent positioning ofsaid housing between occasions of use, said docking station includingpower module and being integrated part of instrument panel of saidvehicle.

Conveniently, said sensor and user communication units are integratedpart of steering wheel of said vehicle.

Advantageously, a pocket-sized handheld unit includes said sensor andcommunication unit with wireless signal communication to said vehicle.

Preferably, wireless signal communication occurs within parts of saidsystem according to industrial standards, e g Bluetooth, ZigBee, RKE.

In order that the present invention may be more readily understood,embodiments thereof will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a flow diagram illustrating the sequence of events for thedetermination of categories according to an embodiment of the presentinvention;

FIG. 2 is a graph of probabilities related to category attribution; and

FIG. 3 is a schematic block diagram of the system architecture for usewith embodiments of the present invention, including the basic elements.

In accordance with embodiments of the present invention, a thirdcategory of driveability is introduced between the blocking andunblocking conditions: With restricted unblocking is meant a conditionin which the moderately intoxicated driver is persuasively informedabout the reason for the restriction and urged to take an informeddecision whether to interrupt the driving operation or not. The reasoncould be moderate alcohol intoxication revealed by the previous breathtest, but could also be due to some unprovoked technical error.

As already inferred, the three categories of driveability of the presentinvention are linked to corresponding categories of alcoholconcentration within a breath sample provided by the driver: Low,moderate and high concentration. By high concentration is meant a levelof intoxication at which a person's judgement is significantly affected.At the other extreme, low concentration, neither a person's drivingcapacity nor his/her judgement are significantly reduced byintoxication. At moderate concentrations, the driver's ability to handlecritical traffic situations is likely to be reduced, however, withremaining sense of judgement, including receptivity to persuasion.

The influence of alcohol on behaviour and capabilities varies from oneperson to another, and may also vary from one occasion to another in anyindividual person. On the other hand, a device controlling driveabilityof a vehicle should preferably operate on the basis of clearly definedlimit values separating the three categories of breath alcoholconcentration. Preferably, the first and second limit values separatingthe three categories differ by a factor of two or more, and coincidewith established legal concentration limits.

In Sweden, vehicle driving is prohibited above a breath alcoholconcentration of 0.1 mg/l, which approximately corresponds to a bloodconcentration of 0.02%. In several European countries, the correspondinglegal limit in terms of breath alcohol concentration is 0.25 mg/l. Aninternational trend towards decreasing concentration limits can benoted. In the present invention, the preferred first concentration limitbetween low and moderate concentration is set at 0.1 mg/l, whereas thesecond concentration limit separating the moderate and highconcentrations is preferably set at 0.25 mg/l.

In the following text, blockings are defined as false when they occurfor a driver with zero alcohol concentration. Correspondingly, falseunblockings are defined as those occurring in a driver with alcoholconcentration at or above the concentration limit (CL), equalling thelimit between moderate and high alcohol concentration, i e thetransition between the unblocking and blocking conditions.

The probability of false blockings and unblockings is closely related tomeasurement errors, and to the location of the trigger level. If theerror distribution is symmetric, and false blockings and unblockings areequally undesirable, the trigger level should be located at half theconcentration limit, resulting in equal probabilities of false blockingsand unblockings. For a normal error distribution with standard deviationσ, the probability of blocking, PB as a function of the alcoholconcentration X normalised to CL can be determined by integrating theerror distribution function:

$\begin{matrix}{{{PB}(X)} = {\frac{1}{\sqrt{2\pi}}{\int_{- \infty}^{X/\sigma}{^{{(\frac{x - {{CL}/2}}{\sigma})}^{2}}\ {x}}}}} & (1)\end{matrix}$

The probability of unblocking PU(X) is simply:

PU(X)=1−PB(X)  (2)

Evidently, the probabilities of blocking and unblocking are criticallydepending on the ratio between the concentration limit and the standarddeviation, CL/σ. More specifically, the expression for falseblockings/unblockings become:

$\begin{matrix}{{{PF}\left( {{CL}/\sigma} \right)} = {1 - {\frac{1}{\sqrt{2\pi}}{\int_{0}^{{CL}/\sigma}{^{{(\frac{x - {{CL}/2}}{\sigma})}^{2}}\ {x}}}}}} & (3)\end{matrix}$

For symmetry reasons, this probability may also be expressed in a formwhich more easily lends itself to numerical calculations:

$\begin{matrix}{{{PF}\left( {{CL}/\sigma} \right)} = {2 \cdot \left\lbrack {1 - {\frac{1}{\sqrt{2\pi}}{\int_{- \infty}^{{CL}/\sigma}{^{{(\frac{x - {{CL}/2}}{\sigma})}^{2}}\ {x}}}}} \right\rbrack}} & (4)\end{matrix}$

Inserting numerical values into eq. (4), probabilities may be calculatedfor different ratios CL/σ. Combining the requirements on measurementerror set by the European industrial standard for alcohol interlocks EN50436-2 with the Swedish legal limit results in CL/σ=3.3, and a falseblocking/unblocking probability according to eq. (2) of 9.5*10⁻². In thepresent invention, the concentration limit is extended by at least afactor of two, thus CL/σ=6.6. The corresponding falseblocking/unblocking probability is 9.7*10⁻⁴, representing a reduction ofapproximately two orders of magnitude.

The dramatically reduced probability of false blockings/unblockings ofthe present invention will to a large extent neutralise the argumentsagainst alcohol interlocks, including the ones concerning personalintegrity, responsibility and undermining of purpose.

The introduction of a third category of driveability is also put to usefor more intelligent handling of technical system errors and attempts atcircumvention. For a comparatively complex system such as that of analcohol interlock, the accumulated probability of technical systemerrors over the vehicle life cycle becomes substantial.

In embodiments of the present invention, a system self test isautomatically executed in conjunction with each breath test. In thesystem self test, possibly provoked or unprovoked errors are beingdistinguished from each other. Unprovoked errors will automatically setthe vehicle into the restricted unblocking condition, whereas a provokederror, attempts at circumvention, or manipulation will lead to ablocking condition. In both cases a specific error message iscommunicated to the driver. The system self test may, in principle,include all functional elements of the alcohol interlock, and will thusprovide adequate protection against circumvention, manipulation ormisuse. Preferably, it is functionally integrated with the breathsampling process with no time delay.

Furthermore, embodiments of the present invention involve integration ofsystem architecture. First, the functional devices may themselves behighly integrated using combinations of semiconductor technologydeveloped for integrated circuits, MEMS (micro electro mechanicalsystems) devices, PSoC (programmable system on chip). Second,structures, components and subsystems already available within thevehicle are being put to use for the system implementation. Theintegrative approach results in significant cost savings with respect toproduction, use and maintenance.

The present invention seeks to provide an essential refinement of thepurpose, function and characteristics of alcohol interlocks. Whenimplemented at an industrial scale, embodiments of the invention areexpected to save human lives and property.

In the following, the term driver will be used to any person in controlof a vehicle, irrespective of intention of, or actually, driving. Theterm road-user will be used to denote any passenger, or other personbeing potentially or actually influenced by the actions of the driver.

The flow diagram of FIG. 1 includes a starting condition 1 activated bya switch or other similar means. The switch may be coupled to thecentral lock of the vehicle, or the ignition key, but may also becompletely independent of the vehicle system. Immediately upon start, asystem test 2 is performed. Normally no errors are detected, since thesystem is designed for high reliability, using high quality componentsand assembly procedures. However, when a system error is detected, itwill either be categorised as an unprovoked error, outside the user'scontrol, or as a possible result of some kind of manipulation. Thesecases will directly set the vehicle in restricted unblocking andblocking conditions 6 or 7, respectively.

The categorisation of errors into provoked or unprovoked is based onbasic criteria described in the table below.

TABLE Categorisation of technical errors. Localisation MechanismCategory External Circuits shorted or Provokable connections openedSensor “window” Blocking, bypass Provokable Internal hardware Componenterror Unprovokable Circuits shorted or opened Software Coding errorUnprovokable User interface Non-compliance with Provokable instructions

The possibility of provoking error, or manipulating the system, isbasically limited to the boundaries of the system with respect to theuser and the vehicle system, which are either located at externalconnections, the “window” represented by the sensors, and the userinterface. Internal error sources related to either hardware orsoftware, are not easily provoked, unless introduced by interventioninto design, programming, or maintenance routines normally inaccessibleto the user.

Since the categorisation of errors is based on rules as outlined in thetable, it may be included in the system test. The detection of a systemerror will thus be shortly followed by its categorisation into provokedor unprovoked, whereby a provoked error will result in blocking, whereasan unprovoked error will result in restricted driveability.

After passing the system test 2 with no errors, the driver is instructedto provide a breath sample 3 which will be analysed with respect to oneor more of duration, volume, flow, pressure, temperature, humidity,carbon dioxide concentration, or other characteristic properties of anexhaled breath sample from a human being. If a breath sample is notaccepted, the driver will be instructed to make a new attempt. Repeatedfailures to deliver breath samples will be interpreted as attempts atmanipulation, which will set the vehicle in the blocking condition 7.This is accomplished by counting the number of attempts, indicated as Nand box 8 in FIG. 1. If accepted, the breath sample will be furtheranalysed with respect to its alcohol concentration 4.

Breath sampling is preferably performed in the vicinity of the driver'smouth after instruction to perform a forced and extensive exhalation inorder to ensure that deep lung air is included. A mouthpiece is notnecessarily used for sampling, since the dilution of a breath sampleobtained in free air may be determined by the simultaneous measurementof tracer signals, preferably carbon dioxide, humidity or temperature.Notably, the composition of alveolar air with respect to these entitiesis remarkably well-defined and stable. Furthermore, they possessspecific timing properties resulting from the presence of dead spacecorresponding to the upper airways. At normal ambient conditions,temperature and humidity are increasing more rapidly than carbon dioxideat the onset of exhalation.

The analysis of alcohol concentration is performed by means of sensingand computational elements. A preferred method is infrared transmissionspectroscopy, in which a beam of infrared light is transmitted from abroadband source to a detector equipped with dispersive element enablingspectral analysis of the transmitted beam. The presence of alcoholwithin the transmission path provides a specific signature of thedetected signal, allowing both substance identification andquantification. The signature is based on molecular properties ofalcohol resulting in specific infrared absorption characteristics.Alternatively, alcohol concentration may be measured by electrochemicalor semiconductor sensors, however, with lower specificity andreliability. Any other suitable arrangement for determining theconcentration of alcohol in the occupant's blood may also be used.

The alcohol concentration is categorised as low, moderate or high,depending on pre-programmed criteria. Low concentration will lead to theunrestricted unblocking condition 5, moderate concentration to therestricted unblocking category 6, and high to the blocking condition 7.

The category of restricted unblocking 6 will include means of persuasionor discomfort, by auditory, visual or haptic stimulation intended toprovoke the attention of said driver. Preferably, the intensity andpersuasiveness of these means will increase with increasing alcoholconcentration, and elapsed time from the breath sample acceptance. Thestimulation is, for example, exerted by flashing source of light,high-intensity tone of sound at audible frequency or infrasound, verbalmessage urging person to stop vehicle, communicated as display text orby artificial voice, vibratory means exerted at or within the driver'sseat, and the activation of warning blinker intended to provoke theattention of other road-users.

In order to ensure that the breath sample is actually originating fromthe driver and not any other person, its acceptance is preferablyinfluenced by signals indicating conditions of the vehicle, includingopening/closure of main lock to said vehicle, opening/closure of door todriver's seat, attachment/detachment of driver's seat belt, and positionof ignition key. In modern vehicles, these signals are normally alreadypresent.

FIG. 2 is a graph showing the unblocking/blocking probabilities as afunction of alcohol concentration normalised to CL. Curves for CL/σequalling 3.3 and 6.6 are included in the figure. As already inferred,CL/σ=3.3 corresponds to realistic performance and limit values. In thepresent invention, the corresponding CL/σ will at least double to 6.6.The graphs shown in FIG. 2 were obtained from numerical calculation ofEq. (2). For CL/σ=3.3 and zero concentration, the blocking probabilityis approximately equals 0.05, which is equal to the probability ofunblocking at concentration=CL. These two probabilities add up to thetotal probability of false blockings/unblockings as already quotedabove. From FIG. 2, the dramatic reduction of the probability of falseblockings/unblockings when increasing CL/σ from 3.3 to 6.6 is evident.

FIG. 3 schematically depicts the architecture of a system embodying theinvention. Preferably, the system is comprised of two physicallydistinguishable block units: The driver interface unit 11, the vehicleinterface unit 12, with electronic communication with the main vehiclesystem 13.

The driver interface unit 11 includes a sensor unit 14 with sensorelements responding to alcohol concentration, and any combination ofcarbon dioxide concentration, humidity and temperature of the breathsample. Preferably, alcohol, carbon dioxide and water vapour (humidity)concentration is measured in a single cavity traversed with infraredradiation from a broadband blackbody source radiator. Different bandpassinterference or diffraction filters tuned to absorption bands specificto alcohol, carbon dioxide and water vapour, are being used in amultiple band infrared detector. The signal outputs from the detectorrepresents concentration of each of these entities. Temperature may bemeasured using thermocouples or resistive temperature sensor.

Typically, the signals from the sensor unit 14 are analog voltages whichrequire conversion into digital format in an analog to digital converter15, before they are transferred to the computational unit 16. This unitincludes means for the execution of pre-programmed arithmetic, logicaland sequential operations, memory unit for temporary or permanentstorage of information. The computational unit 16 is thus capable ofexecuting the operations outlined in FIG. 1, provided that eachoperational step has been adequately defined, compiled and stored in theprogram memory.

Also included in the driver interface unit 11 is an output device in theform of a user communication unit 17 for the display or transfer ofinformation relevant to the driver and receiving input control signalsfrom the driver. The communication unit may also include means foraudible or haptic signal communication.

The driver interface 11 accommodating sensor and user communicationunits 14 and 17 is preferably packaged in a housing adapted forsingle-hand operation by the driver. In a preferred embodiment thesensor and user communication units 14 and 17 constitute integratedparts of the steering wheel of the vehicle. Signal and power lines arepreferably communicated along the steering shaft. Alternatively, signalsare communicated by wireless link, preferably using commonly accessedradio frequencies and protocols according to industrial standards, suchas Bluetooth or ZigBee.

The driver and vehicle interfaces 11 and 12 are electronicallycommunicating by means of interface circuitry 18, 19 via a communicationchannel 20. Preferably, the communication is performed in a serialdigital format, and encoded in order to prevent manipulation. Basically,the vehicle interface unit 12 relays the communication between thedriver interface 11 unit and the vehicle system 13 for the control ofsaid driveability categories, and performs a supervisory system functionin relation to the system self test described above. In order to executethis supervisory function, the vehicle interface is equipped with acomputational unit 21, sensor and actuator units 23, 24, and a displayunit 22.

The vehicle interface 12 communicates with the vehicle system 13 bymeans of a communication channel 27, and interface circuitry 25, 26.Preferably, the communication channel 27 conforms to standards forvehicle signal communication by e g the CAN bus arrangement.Alternatively, signals are communicated by wireless link, preferablyusing commonly accessed radio frequencies and protocols according toindustrial standards, such as Bluetooth or ZigBee.

The system according to the invention is preferably directly orindirectly powered from the main vehicle power supply 28. The directpowering makes use of permanent power lines to each active unit asillustrated in FIG. 3. Indirect powering may involve rechargeablebattery built into one or several units, e g the driver interface 11.

Preferably, blocking of the driveability of the vehicle according to thecategory described above is controlled by actuation onto ignition key,solenoid, start motor, fuel injection unit, steering wheel, or gearcontrol. In order to make manipulation more difficult, actuation of morethan one of these functions are being performed simultaneously, butdifferently at different occasions. The control of which functions areactuated at any one occasion is preferably stored in the program memoryof the computational units 16 or 21.

The restricted unblocking category of driveability is implemented by anumber of persuasive signals directed to the driver. These signals maybe activated via the user communication unit 17, or elements included inthe vehicle unit 13, e g the warning blinker.

The physical implementation of the system according to the invention maytake several alternative forms. In a preferred embodiment, the driverinterface unit is embedded into a housing adapted for single-handoperation by the driver. The housing is accommodating the sensor,computational and user communication units 14, 16, and 18. The housingis adapted to a docking station for permanent positioning betweenoccasions of use. The docking station includes power module and is anintegrated part of the instrument panel of the vehicle. The dockingstation includes the vehicle interface unit 12.

In another preferred embodiment, the driver interface unit 11 isembedded within a pocket-sized handheld unit including sensor,computational and communication units 14, 16, 18. According to thisembodiment, the pocket-sized unit is communicating with the vehicleinterface 12 via a wireless link, preferably using standard frequenciesand protocols according to the industrial standards for remote keylessentry (RKE). In this case, simplex rather than duplex communication canbe used, reducing cost and improving user friendliness.

When used in this specification and claims, the terms “comprises” and“comprising” and variations thereof mean that the specified features,steps or integers are included. The terms are not to be interpreted toexclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the followingclaims, or the accompanying drawings, expressed in their specific formsor in terms of a means for performing the disclosed function, or amethod or process for attaining the disclosed result, as appropriate,may, separately, or in any combination of such features, be utilised forrealising the invention in diverse forms thereof.

1. A vehicle safety system, comprising: an alcohol concentrationdetermining arrangement, for making a determination as to theconcentration of alcohol in the blood of a vehicle occupant; a controlunit adapted to receive and analyze data from the alcohol concentrationdetermining arrangement to create an analysis, and in dependence uponthe results of the analysis, the control unit being operable to outputone of a blocking signal and a dissuasion signal; a blockingarrangement, adapted to receive the blocking signal and to preventdriving of the vehicle by the vehicle occupant; and an output deviceadapted to receive the dissuasion signal and to present at least onewarning to the vehicle occupant to dissuade the occupant from drivingthe vehicle; wherein: the control unit is operable to categorize theconcentration of alcohol in the occupant's blood into one of threecategories, the categories including a low concentration category, inwhich the blocking signal will not be generated, a high concentrationcategory, in which the blocking signal will be generated, and anintermediate category, in which the blocking signal will not begenerated and the dissuasion signal will be generated.
 2. The systemaccording to claim 1, wherein the alcohol concentration determinationarrangement is operable to analyze a sample of the occupant's breath. 3.The system according to claim 1, wherein the warning output by theoutput device comprises at least one of auditory, visual and hapticstimulation.
 4. The system according to claim 3, wherein the warning ofthe output device comprises at least one of the following: illuminationof a light source, generation of a sound, generation of a verbalmessage, display of text, and vibratory stimulation of a part of thedriver's body.
 5. The system according to claim 3, wherein the warningof the output device varies depending upon the concentration of alcoholin the occupant's blood.
 6. A method of controlling vehicle systems,comprising: determining a concentration of alcohol in the blood of avehicle occupant to identify a determined concentration; categorizingthe concentration of alcohol in the occupant's blood into one of threecategories, the categories including a low concentration category, anintermediate category, and a high concentration category; preventing thedriving of the vehicle by the occupant if the determined concentrationof alcohol in the blood of the occupant is categorized in the highconcentration category; and allowing the vehicle occupant to drive thevehicle and presenting at least one warning to the vehicle occupant todissuade the occupant from driving the vehicle if the determinedconcentration of alcohol in the blood of the occupant is categorized inthe intermediate category.
 7. The method according to claim 6 wherein,if the determined concentration of alcohol in the occupant's blood iscategorized in the low category, a warning is not presented to thevehicle occupant.
 8. A computer program comprising computer program codeconfigured to perform the following steps when the code is run on acomputer: determining a concentration of alcohol in the blood of avehicle occupant to identify a determined concentration; categorizingthe concentration of alcohol in the occupant's blood into one of threecategories, the categories including a low concentration category, anintermediate category, and a high concentration category; preventing thedriving of the vehicle by the occupant if the determined concentrationof alcohol in the blood of the occupant is categorized in the highconcentration category; allowing the vehicle occupant to drive thevehicle and presenting at least one warning to the vehicle occupant todissuade the occupant from driving the vehicle if the determinedconcentration of alcohol in the blood of the occupant is categorized inthe intermediate category; and not presenting a warning if thedetermined concentration of alcohol in the occupant's blood iscategorized in the low category.
 9. The computer program according toclaim 8, wherein the program is embodied on a computer readable medium.